Planets being formed?

This has been an interesting period for planetary science. In the last post, I mentioned the landing of Philae on a comet. As an update, unfortunately all has not gone well. The comet landed well, it bounced, and ended up in a shady spot, do most of what it has managed has relied on batteries. We do not know yet what data it has sent back, so we have no real idea on how successful the venture was, but from my point of view, the news is less good. In my last post, I mentioned that I would like to see what was encased in the ice. What happened was that Philae left it to the last to drill down (because they were afraid that the action of the drill might launch Philae back off the comet, as its gravity is very weak) and they wanted to do as much as they could before that risk was taken. They drilled, but apparently the drill hit something very hard, and when they withdrew the drill and tried to analyze its core, it appeared that there was no sample inside the drill. This is one of the curses of this sort of work. When designing some form of robot, you have to guess exactly what conditions you will meet.

However, a most interesting image has also been released by the European Space Agency. The star, HL Tauri has been found with an accretion disk around it. The star is about 1 million years old, and the disk has rings in it, with dark gaps between them. The most obvious cause for such rings would be the formation of planets, although that does not mean there is a planet in every gap, because while a planet will clear out dust on its path, gravitational resonance will also clear out material. Gravitational resonance is a term for when the orbital period at a given position is an exact multiple/fraction of another. Thus if the planet had a period, say, 12 years (roughly Jupiter’s “year”) there would be 2:1 resonances at a distance where the orbital period was 24 years, or at a distance where the orbital period was 6 years. Where this happens, over a period of time the various gravitational effects, instead of cancelling and circularizing, tend to reinforce and the bigger object causes the very much smaller one to change orbit.

So, are there planets there? One answer is, we don’t know because we have not seen them. Up to a point, this is a bit of a negative in this case. At first sight it may seem obvious that we would not see planets because they are too dull, but that is not the case with very newly formed giants. Thus there is a star HR 8799 and we can see four giant planets around it. The reason we can see them is that they are newly-formed giants, and when they take up the gas, the gravitational energy of the gas falling onto the planet heats it to a yellow-white heat, and the planets glow relatively brightly. Given we cannot see planets here, but we can see the disk, what does that mean?

One obvious thing that it can mean is that planets have yet to get big enough to glow brightly. In my theory of planetary formation (Planetary Formation and Biogenesis) our star had to have formed its planets by about 1 million years. The reason for this assessment is that there is a star LkCa 15 that is 3 million years old, and it has a planet much bigger than Jupiter, and significantly further from the star. Planetary growth should be faster, the closer to the star, at least for the same sort of planet, because the density of matter increases as it falls into the star. (The circumferences of the orbits decrease, and if the same amount of matter is presence, there much be more per unit volume.) Incidentally, we know about the planet around LkCa 15 because we “see” it, at least in images obtained by powerful telescopes, so it is glowing. Since we only see one giant, my theory requires there to be three other giants we cannot see, presumably because they are yet of insufficient size to glow sufficiently brightly for us to image them. So, if I am right, 1 My gets you giants of the size we have, and the longer the disk lasts, the bigger the giants get.

All of which shows there is still a lot of interest in planetary research

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Philae, the comet, news reports, and the possibility of another planet.

The big news on the science front this week was the landing of Philae on a comet, and I found it interesting to note how the news media reported it. One of the most fascinating things for me was the announcement of the comet’s velocity. Yes, it is travelling very fast, but what is important when it came to landing on the comet is not how fast the comet is going, because that is meaningless. The important thing to consider is the relative velocity of Philae and the comet, and that was rather small.

There is no absolute velocity; velocity only has meaning when you consider it in the frame of reference of something else, in which case it is called the relative velocity. It is from this sort of thinking that we get relativity, the first version of which came from Galileo when he noted that if you are inside a ship you cannot tell how fast you are going – and even outside the issue is questionable. Outside, you can see how fast you are travelling relative to the water, but the water may be travelling relative to the land. In the case of trying to land a vehicle on a comet, the trick was to match the mother ship’s velocity as near as possible to that of the comet, and then let Philae approach and land at a relatively small change of velocity. In fact the hardest part of this was not to get Philae safely down, but rather to keep it down. The danger was always that it would bounce off, as the comet has only an extremely small gravitational force. In fact it appears that Philae did do some bouncing, and unfortunately it landed in a shady spot from where it cannot easily recharge its batteries through its solar cells. That means the information we get back will be dependent on what it could do for the day or so the original charge in the batteries lasted.

So, what will Philae tell us, assuming all goes well with its experimental equipment. We probably will not get an analysis of gas coming off the comet, because gas emissions probably do not get underway sufficiently well until the comet gets closer to the sun. However, we should get a good account of the composition of the very top surface of the comet. Unfortunately, that may not be very informative because the interesting more volatile material has probably been given off on previous encounters with the star, and any organic material there will have been subjected to considerable UV radiation. Comets spend their lives in very cold places, and the colder the site, the slower chemical reactions are (although this does not apply to photochemistry, because the energy to get these started comes from the light). The problem is, the comets would have formed when the solar system formed, which was 4.5 billion years ago, and while such reactions might be slow, 4.5 billion years remains a long time.

I have seen some reports saying that it will show that comets brought water to Earth. It will show nothing of the sort. At best, it might show comets are a possible source, but the evidence that we have so far is that cometary water has too much deuterium in it, so that is not where our planet’s water came from. It might have organic molecules in it, such as amino acids. It might, but that does not mean that is where the chemicals that permitted life to form came from. These issues are very complicated, and for those interested, I outlined the issues in my ebook Planetary Formation and Biogenesis.

Finally, what I would like to see is evidence of neon secreted into the ices. My mechanism for how planets accreted involves the melt fusion of bodies with a particular ice encased in water ice acting as the fusing agent. The mechanism is a little like that of forming snowballs, and the outer giants in this solar system are predicted to total four, based on four different temperature ranges of known ices. However, there is a possible fifth: neon. Was neon encased in ice? For neon to act as such an agent, the ice probably had to be below fifteen degrees above absolute zero as it started to approach the star. Would it? If it did, the comet might contain neon, but whether we can detect it is another matter because any such neon would have been lost from the surface of the comet in previous stellar encounters. Degassing from the centre might show it, but Philae probably won’t have the power to tell. For me it is important because if neon was encased in the ices that were in our accretion disk, then there is a possibility of another planet out there, probably in the order of 3-4 times further from the sun than Neptune. It would be a lot smaller than Neptune (because growth there is slower because everything is more dilute) so it would not be easy to find, but it would be nice to know if there were a reason to look for it.

Materials for the first Martian settlers

In the previous post, I discussed the difficulties settlers on Mars might have with making things to construct domes, etc in which to grow food. Now, let’s suppose they have got that under control, where are the next difficulties? The settlers have a place to live, they have grown food in their domes, but they still have to cook it. Yes, we have energy (assuming all has gone well) but there are other things as well, assuming the settlers want more than the ability to survive. For example, in cooking there is often a lipid, such as olive oil or butter used. Even assuming they have big enough domes, are they going to wait around for olive trees to grow? Fortunately there is a way out of this. Microalgae have lipids in them, and if we grow them then mature them in a nutrient deficient solution, the oil content can rise to over 60% by weight. If there are plenty of nutrients, then the microalgae grow very rapidly (more rapidly than most plants) and largely contain protein, which makes them a desirable food, but for two things: the taste, and the fact they have a rather high content of nucleic acids. In my novel Red Gold, set in a proposed colonization of Mars, I suggested there would be a variety developed with much lower nucleic acid content. I suggested the settlers would start off by eating a lot of chlorella because it takes a long time for plants to grow.

Another problem the settlers will have involves clothing. Clothing is made from fibres and most fibres now come from the oil industry. Of course we can get free of synthetic fibres by returning to cotton and linen, which come from plants, as long as someone remembers to take them. But if settlers are going to do that, they will be growing a lot more than they are eating. Wool would not be available in most scenarios because sheep need a significant area to graze on, and that means building giant domes, AND finding enough material to make soil. Eventually, as they start growing crops, the dead waste plant material will be used to make more soil, but it will be gradual. Soil means more than “dirt”. Then, after that, they will still need polymers from the chemical industry to make suits that can be used for going outside, because it is important to be able to seal the air in the zone in which you intend to breathe. Where do they get the raw materials for such polymers? They will have to take something that will generate them. As it happens, chlorella can be processed to help make some such polymers.

Speaking of dirt, settlers may want to wash. Yes, you can wash in just water, to some degree of efficiency, but you might want soap. Can they make that there? Soap is made by treating lipids with caustic soda, whereupon you make soap and glycerol. Needless to say, you have to get the ratio of caustic soda right. Interestingly, pioneers often did this on Earth. I can recall as a boy, my father elected to do what his father had done, and make soap in the back garden. The family carefully kept the fact from roasts, clarified it, and it was heated up in a kerosine tin (4 gallons) in the back yard, then the caustic soda was added. This was largely used for laundry. The point is, soap making is not difficult, although it is more so if you want quality. But this brings up another point: when settlers get to Mars, they will have to do just about everything themselves, and unlike pioneers on Earth, there is no grass ranges, nor forests for timber. Worse, many of the things we take for granted involve several steps. Even for soap, the settlers first have to find and mine salt, then they have electrolyse that (doing something with the chlorine that is also made) then they have to react that with lipids that have been collected and purified, then they have to separate out the glycerol and do one or tow things to make an attractive cake. Most things we take for granted have a lot more steps, each requiring a specific skill. There are just so many things to do that involve a lot of different skills that you need a reasonably large number of people to do them. But then you have to take an awful lot of stuff to sustain all these settlers while they get going.

Perhaps now you see the trend of what I am trying to say. The cost of lifting stuff from Earth into space is horrendous, so settlers on Mars simply could not afford to purchase anything other than the most valuable materials from Earth. They have to make everything they want there, except possibly the most valuable pharmaceuticals, and there are very few raw materials that are easily obtained there. Life for such a settler would be extremely spartan, and it will not work unless there are a number of skilled people to carry out the tasks that require advanced technology.

Energy for Martian settlers

In a previous post on colonizing Mars, the question of energy arose. How would we generate energy on Mars? There are more issues here than is immediately apparent, because in thermodynamics we see a clear distinction between heat and work, there is the issue of energy and power density, and there is the issue of portability. The forms we use on earth that we cannot use on Mars include burning fossil fuel (there is none, and no significant oxygen to burn it in), hydro and tidal (because there is no liquid water), geothermal (because we do not know where any fields are, if there are any) or wind (because atmospheric pressure is too low for it to be useful). We can use solar, except the power density during the day is only half that on earth, which means we have to have twice the area of solar cells to get the same effect. This will be fine for electric lighting, or other light uses, but it will not provide a high power density, and you need batteries to store the electric energy. What happens when the batteries need replacement? Nuclear fission and nuclear fusion would be available, always assuming we had developed nuclear fusion technology.

The settlers need continual low-grade heat (because the temperature on Mars is generally below freezing temperature) electric power for working machines, some form of transport fuel, and very high energy density for making things. It is this high-density power that is the problem, and it would seem that nuclear energy, fission or fusion, is required. That in turn requires the settlers have adequate engineers to fix things if they go wrong.

How do we make materials? There are two problems, as illustrated by trying to make iron. The obvious one is to get it hot enough to melt and cast objects (although with 3D printing, you may merely want a powder). But the other is how to get the metallic iron in the first place. One of the problems with Mars is that there has not been a lot of chemical action, as far as we know. At the Meridianum Planum, we know there is some haematite, but generally the iron and most other metals are present in the form of silicates. Silicates are very difficult to break up. Earth has broken them up through chemical weathering, by which carbon dioxide dissolves in water and makes carbonic acid, which in turn very slowly breaks down basaltic type rocks to form silica, and iron and magnesium carbonates. The carbonates have subsequently either been oxidized (basalt contains FeII, but then is oxidized by air to Fe III, and on earth we end up with large deposits of the oxide Fe₂O₃ that are the major sources of iron ore now, and were deposited from ancient oceans almost three billion years ago when oxygen started to be made by plants. The magnesium has ended up being dissolved and is recovered from sea-water as magnesium sulphate. However, it is not clear whether Mars has had water for long enough to do this. One clue is that when these weathering processes go on, the calcium ends up as limestone. Our admittedly limited survey of Mars has failed to find significant iron or calcium carbonate.

If we were to get some oxides, on earth we reduce those with carbon, but that won’t work on Mars because we are short of carbon. (No coal. We could eventually make charcoal, but it would take some time to grow enough biomass to do that, and of course we have to have the energy to make the charcoal.) We might also want to make glass. Besides having to melt it, we need the raw materials, and they are not readily found, and probably not at the same place. Either we tear silicates to bits, or we have to do a lot of exploration to find the various basics we need. Worse, if we use something like nuclear power to get the energy density, then that has to be somewhere at a distance, and you will need a lot of electric cable. If everything has to be brought from earth, it is going to be a very expensive settlement. In my novel, Red Gold, I had my colonists simply tear apart dust and separate the elements by electromagnetic fields, the same way a mass spectrometer works. That would require extreme energy, and for that I used the two fusion motors that drove the first ships there. That is extreme, and better for fiction, but the point remains, how are settlers going to get raw materials? If the settlers do not have an answer, very soon they will die. This leads to a conclusion: any settlement on Mars will require nuclear fission or fusion to be viable in the longer term. A second conclusion I had for Red Gold is that when making raw materials, the most predominant materials that will be made include iron, aluminium, magnesium and silica. Silica is necessary for glass, in turn needed for glass-houses, while the other metals would be useful for construction, so all is not lost.

Meanwhile, a reminder that Red Gold, and in the UK the first two of my Gaius Claudius Scaevola ebooks are available on promotion over the weekend. (In the US, only the second, Legatus Legionis is on promotion, thanks to an error on my part.)